1. Field of the Invention
This invention relates to wireless communication systems, particularly point to multi-point (PMP) and mesh or mobile ad-hoc networks (MANET).
2. Discussion of the Known Art
Point to multi-point or PMP protocol communication equipment is used in various broadband wireless systems. The systems are typically standards-based, or are certified by industry trade groups, e.g., WiMAX Forum certified, IEEE 802.16-2004, IEEE 802.16d, IEEE 802.16e-2005, IEEE 802.16e, and HIPERMAN.
Communication equipment operating under mesh or mobile ad hoc network (MANET) protocols is often used in military applications. An example of a mesh network is given in the original IEEE 802.16d standard which, in addition to a PMP mode, defined a mesh mode as well. The standard allowed for only one of the two modes to be selected for network operation, and did not allow for both modes to operate simultaneously. See, e.g., F. Jin, et al., Routing and packet scheduling in WiMAX mesh networks, Fourth International Conference on Broadband Communications, Networks and Systems, BROADNETS (2007). The mesh mode, which was in subclause 6.2 of the original IEEE 802.16 standard, was withdrawn from the latest version (May 29, 2009) of the standard, however.
Allocations of new radio frequency (RF) bands for operation of wireless communication networks are often difficult to obtain. Because of this and for other reasons, it would be desirable to allow multiple network topologies or protocols (e.g., PMP, and mesh or MANET) to co-exist on any one channel or channels of a wireless network without causing interference among different communications taking place under each protocol. For example, a relay station (RS) may need to extend the coverage of an existing wireless PMP base station (BS) in order to allow a given node outside the existing coverage to join the network as a new subscriber station. In such a case, the BS and the RS could link with one another using the mesh protocol to coordinate the use of network channels, and thus allow the RS to operate as a PMP base station with respect to the new subscriber station.
In another example, two military convoys each employing a PMP system may need to maintain wireless connectivity between vehicles of their respective convoys while in motion. As the base stations of the two convoys pass near one another, it would be desirable for the two base stations to implement a MANET in order to coordinate their movements with one another while maintaining their individual PMP networks.
Yet another example is a military training exercise in which it becomes necessary to gather performance data from thousands of RF collection devices in the field. Each soldier may be provided with a wireless device for relaying data collected during the exercise. Such devices would operate most efficiently in a PMP network, but some of the devices might be outside PMP coverage and need to forward data through other wireless devices (other than a BS) so as to maintain connectivity. Again, a MANET or mesh network operating simultaneously on the same channel with the PMP network would meet such a need. The foregoing examples are merely illustrative and are not intended to limit the various circumstances in which the present invention may be used advantageously.
U.S. Pat. No. 7,031,274 (Apr. 18, 2006) discloses a method of enabling systems following the IEEE 802.11 protocol to interoperate with wireless local area networks (WLANs) that use an otherwise incompatible HIPERLAN/2 standard, on a common transmission channel. Further, U.S. Pat. No. 7,133,381 (Nov. 7, 2006) describes a method by which stations operating under an enhanced, IEEE 802.11e standard, can prevent interfering transmissions from stations that do not practice the 802.11e standard.
U.S. Pat. No. 7,630,402 (Dec. 8, 2009) discloses a media access control unit with specified software and hardware for the purpose of implementing the mentioned IEEE 802.16 standard protocol. The patent does not suggest any variance to the protocol such as would allow both PMP mode and mesh mode communications to occur simultaneously on an IEEE 802.16 standard wireless network, however.
U.S. Pat. Appl'n Pub. No. 2008/0151802 (Jun. 26, 2008) concerns power saving techniques within an IEEE 802.16 network including relay stations (RS) as defined by the IEEE 802.16j standard, wherein end users (mobile and fixed) may conserve power and achieve longer battery life. A “MAP” structure is received at a RS and modified prior to retransmission to effect better power utilization in the network. The publication does not suggest any change to the underlying IEEE 802.16/802.16j network “tree” protocol wherein a source node must pass its information to nodes on higher branches which, in turn, distribute the information to lower branch nodes until the information reaches the destination node, even if the source and the destination nodes are in range and could otherwise communicate directly with one another.
U.S. patent application Ser. No. 11/998,356 filed Nov. 29, 2007, and assigned to the assignee of the present application and invention, discloses a process and system for enhancing connectivity among nodes in a wireless network with changing topology, wherein certain nodes are configured to change roles by operating in (i) an ad hoc or mesh mode, (ii) a point-to-multipoint mode, or (iii) both modes simultaneously, in order to maintain optimum connectivity among all nodes of the network. The '356 application was published as US 2009/0141653 on Jun. 4, 2009.
U.S. Pat. Appl'n Pub. No. 2002/0027894 (Mar. 7, 2002) describes a hierarchical network structure having a three tier structure similar to the existing Internet or phone system, wherein wired links are replaced with wireless links and the top two tiers are static and pre-configured. A common “multi-radio” approach is implemented wherein IEEE 802.11 is adopted for mesh communications, and IEEE 802.16 is used PMP communications. That is, different communications protocols for are used for the different tiers. See also, U.S. Pat. Appl'n Pub. No. 2006/0083205 (Apr. 20, 2006) which discloses the concept of a coordinated access band (CAB), wherein requests for dynamic access to the CAB spectrum are mediated and time-bound rights are granted for use in either a cellular or an ad hoc mode.
As far as is known, no one protocol has been proposed that will enable PMP and mesh/MANET communications to occur simultaneously over one or more shared channels of a wireless network (including networks that follow the IEEE 802.16 standard or are WiMAX based), while avoiding interference between the two modes of communications on a given channel or channels. Note that IEEE 802.11 has a PMP protocol of sort (called PCF) which is not generally practiced or employed. PCF differs from other PMP networks such as WiMAX, however, and techniques for using PCF in IEEE 802.11 networks cannot be applied in other PMP networks.